The present invention, in some embodiments thereof, relates to medical application and, more particularly, but not exclusively, to a method and system for monitoring sleep.
Apnea is a Greek word meaning “without breath” which is used in the literature to describe a condition of a temporary pause in breathing. Sleep apnea refers to the temporary cessation of breathing during sleep. Sleep apneas have been classified into three types: obstructive sleep apnea (OSA), central sleep apnea (CSA) and mixed sleep apnea (MSA). The difference between obstructive sleep apnea and central sleep apnea is that in obstructive sleep apnea the breathing passageways are blocked, while in central sleep apnea the neural drive to respiratory muscles is transiently abolished but the passageways can still be open. In central sleep apnea the lungs form a reservoir for air flow even though the individual is not breathing.
Mixed sleep apnea consists of a central sleep apnea component and an obstructive sleep apnea component. In mixed sleep apnea, the obstructive component typically follows the central component. The most common type of sleep apnea is obstructive sleep apnea.
Also known are obstructive sleep hypopnea, which is a milder form of obstructive apnea characterized by partial obstruction of the upper airway passages, and central sleep hypopnea, which is a milder form of central sleep apnea characterized by shallow breathing while the upper airway are open.
An apnea event generally leads to a progressive-type asphyxia until the individual is briefly aroused from the sleeping state, thereby restoring airway patency or respiratory muscles activity thereby restoring airflow to the lung. Consequently, sleep of individuals diagnosed with sleep apnea is fragmented and of poor quality.
Sleep apneas, particularly of the obstructive type, are recognized as life-threatening conditions. Individuals with sleep apnea have an increased risk of suffocating during sleep or during surgery requiring general anesthesia.
Sleep apnea is diagnosed using a test called Polysomnography (PSG), which involves the patient sleeping in a sleep lab connected to various measurement instruments. The test provides an Apnea/Hypopnea Index (AHI) which drives a diagnosis of sleep apnea along with severity.
When an individual is diagnosed with sleep apnea, the individual may be prescribed a therapeutic regime involving the use of a Continuous Positive Airway Pressure (CPAP) device. The CPAP device works by delivering a steady flow of air through a soft, pliable mask worn over the individual's nose. The CPAP device essentially pressurizes the throat of the individual thereby preventing the collapse of the soft tissue and keeping the airways open and allowing the individual to breathe uninterrupted during sleep.
For more severe cases of OSA, surgery such as laser assisted uvuloplasty is used to provide a partial treatment. Additional types of treatments are disclosed in U.S. Pat. Nos. 5,988,171, 6,250,307, 6,523,542, 6,431,174 and 6,601,584.